Early in the COVID-19 pandemic, scientists noticed that a SARS-CoV-2 infection can “wake up” other, dormant viruses already present in the body. A new study extends those and subsequent observations, documenting viral reactivation for a cohort of more than 1000 patients hospitalized with COVID-19 before mid-2021. The findings provide a detailed picture of the hidden viruses that become active at different points of a SARS-CoV-2 infection, and link reactivation of some of them to more severe C